◊ BACKGROUND:
Meperidine has been shown to exhibit a sensory block in peripheral nerves. However, its motor blockade ability is controversial. The aim of this study was to investigate, electroneurographically, the ability of meperidine to inhibit conduction in both sensory and motor fibres in the ulnar nerve.
◊ MATERIALS AND METHODS:
The study was conducted in a double-blind, placebo-controlled fashion. Eighteen healthy volunteers were randomized into three groups (Saline, meperidine 1% and meperidine 2%). Three millilitre of the study solution was administered to the ulnar nerve perineurally at the level of the wrist by the guidance of a nerve stimulator. Sensory nerve action potential (SNAP) and compound motor action potential (CMAP) amplitudes were recorded. At least a 20% decrease in the initial response amplitude was accepted as a block.
◊ RESULTS:
The number of individuals with sensory and motor block with saline, meperidine 1% and meperidine 2% were 0/6, 6/6, 6/6 and 0/6, 5/6, 6/6, respectively (P<0.05). The maximum decrease in the median SNAP and CMAP amplitude values were 4.7% and 8.3% with saline; 38.5% and 46.4% with meperidine 1%; and 100% and 97.8% with meperidine 2%, respectively (P<0.05). Median values for the duration of sensory and motor block with meperidine 1% and meperidine 2% were 45, 52.5 and 30, 32.5 min, respectively.
◊ CONCLUSIONS:
Meperidine blocks sensory and motor nerve conduction in a dose-related manner.
◊ Reviewed by R. Stienstra, MD. PhD.
Nijmegen, The Netherlands
This study confirms that meperidine has local anaesthetic properties and is capable of inducing both sensory and motor block of the ulnar nerve at doses of 30 to 60 mg.
The question is whether this is of any clinical relevance. Obviously, there is no point in completely replacing a local anaesthetic with meperidine: There is no immediate advantage, and the meperidine dose would have to be so high that systemic side effects will become unacceptable. The authors suggest that adding (a low dose of) meperidine to a short- or medium-acting local anaesthetic may be beneficial in terms of reducing motor block while preserving sensory block. I seriously doubt that, as the duration of sensory block with both doses of meperidine (30 mg and 60 mg) in this study was less than 1 hour, i.e. shorter than a short-acting local anaesthetic. Therefore it seems that while the data are interesting from a scientific perspective, the clinical implications are minimal to absent.
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